Evaporator structure in absorption refrigeration



Feb. 22, 1955 w. G. K6651. ET AL 2,702,457

EVAPORATOR STRUCTURE IN ABSORPTION REFRIGERATION Original Filed Feb. 26,1949 5 Sheets-Sheet 1 w llwflyolv w M @53 y W M MJTTORNEY Feb. 22, 1955w. G. KCGEL ET AL 2,702,457

EVAPORATOR STRUCTURE IN ABSORPTION REFRIGERATION Original Filed Feb. 26,1949 5 Sheets-Sheet 2 III '0'"; iiilin IIIIII. '1

INVENTORS a M W ATTORNEY Feb. 22, 1955 w. ca. KOGEL ET AL 2,702,457

EVAFORATOR STRUCTURE IN ABSORPTION REFRIGERATION Original Filed Feb. 26,1949 5 Sheets-Sheet 3 ATTORNEY Feb. 22, 1955 w. G. KOGEL ET ALEVAPORATOR STRUCTURE IN ABSORPTION REFRIGERATION 5 Sheets-Sheet OriginalFiled Feb. 26. 1949 Zia BY flaw/Z WA'TTORNEY Feb. 22, 1955 w. G. KCGELET AL 2,702,457

EVAPORATOR STRUCTURE IN ABSORPTION REFRIGERATION Original Filed Feb. 26,1949 5 Sheets-Sheet 5 w JTTORNEY United States Patent EVAPORATORSTRUCTURE IN ABSORPTKON REFRIGERATION Wilhelm Georg Kiigel, Stockholm,and Gunnar Axel Grubb, Bromma, Sweden, assignors to Aktiebolagetglektrolux, Stockholm, Sweden, a corporation of weden Originalapplication February 26, 1949, Serial No. 7 8,502. Divided and thisapplication August 23, 1952, Serial No. 305,966

Claims priority, application Sweden March 2, 1948 Claims. (Cl. 62-95)This invention relates to refrigeration and is especially concerned withrefrigerators of the absorption type employing an inert gas or pressureequalizing agent. More particularly, the invention is concerned withdistributing refrigerating efiect in absorption refrigerators of thistype having a plurality of evaporators or cooling elements operable atdifferent temperatures. This application is a division of our copendingapplication Serial No. 7 8,502, filed February 26, 1949, now abandoned.

It is an object of the invention to provide improvements for coolingadjacent spaces or sections of a refrigerator with the aid ofevaporators or cooling elements of refrigeration systems of the abovetype which are operable at difierent temperatures, particularly torestrict and retard an increase in temperature in one of the sectionsupon increase in load on the other section.

Another object of the invention is to effect cooling of one of thespaces or sections of the refrigerator with the aid of a low temperatureevaporator which makes use of a cold accumulator, whereby saferefrigerating temperatures will be maintained not only in such space orsection but also in another space or section which is cooled by a highertemperature evaporator connected to receive inert gas partially enrichedin refrigerant from the low temperature evaporator.

The above and other objects and advantages of the invention will be morefully understood from the following description taken in conjunctionwith the accompanying cllrawings forming a part of this specification,and of whic Fig. 1 illustrates more or less diagrammatically anabsorption refrigeration system of the inert gas type to which theinvention is applied;

Fig. 2 is a fragmentary front elevation looking toward the rear of astorage space of a refrigerator embodying the invention, partly brokenaway and in section, the cooling unit being adapted to be connected inan absorption refrigeration system like that diagrammatically shown inFig. 1;

Fig. 3 is a horizontal section taken at line 3-3 of Fig. 2 to illustratethe construction more clearly;

Fig. 4 is a fragmentary side sectional view of a refrigeratorillustrating another embodiment of the invention;

Fig. 5 is a sectional view, taken at line 5-5 of Fig. 4, to illustratethe cooling unit and connections thereto more clearly;

Fig. 6 is a fragmentary sectional view taken at line 66 of Fig. 5;

Fig. 7 is a front elevation, partly broken away and in section, of therefrigerator shown in Fig. 6; and

Figs. 8 to 12 inclusive are fragmentary front elevations ofrefrigerators, partly broken away and in section, illustrating furtherembodiments of the invention.

In absorption refrigeration systems of the inert gas type havingevaporators adapted to operate at difierent temperatures, suchevaporators or cooling elements are usually formed of piping which areshaped as coils and connected by conduits to other parts of the system.In a household refrigerator of the kind in which the interior issubdivided into a plurality of compartments one above 2,702,457 PatentedFeb. 22, 1955 and constructed to provide a maximum amount of usablestorage space in the interior of the refrigerator.

One manner of employing a plurality of such horizontally disposedevaporator coils 10 and 11 in accord with the invention is shown inFigs. 2 and 3. The evaporator coils 10 and 11 are disposed in aninsulated interior 12 of a refrigerator cabinet 14 adapted to be closedby a door or closure member (not shown) which is hinged to the front ofthe cabinet. The evaporator sections 10 and 11 form part of anabsorption refrigeration system of the inert gas type which is more orless diagrammatically illustrated in Fig. 1. In order to simplify thedrawings, the horizontally disposed evaporator coils 10 and 11 of Figs.2 and 3 have simply been shown as straight conduit sections in Fig. 1which are connected by a vertical bend 15.

In a system of the type illustrated in Fig. 1 a refrigerant fluid, suchas liquid ammonia, for example, is introduced through a conduit 16 intothe evaporator sections 10 and 11. In the evaporator sections 10 and 11refrigerant fluid evaporates and diifuses into an inert gas, such ashydrogen, for example, to produce refrigeration and abstract heat fromthe surroundings. The resulting gas mixture of refrigerant and inert gasflows from the evaporator sections 10 and 11 through an outer passage 17of a gas heat exchanger 18 and vertical conduit 19 into an absorbercomprising a vessel 20 and a looped coil 21. In the absorber vessel 20and coil 21 refrigerant vapor is absorbed by a suitable absorbent, suchas water, for example, which is introduced into coil 21 through aconduit 22. The hydrogen or inert gas, which is practically insolubleand weak in refrigerant, returns to the evaporator sections 10 and 11through an inner passage 23 of the gas heat exchanger 18 and a conduit24-.

The circulation of gas in the gas circuit just described is due to thedifference in specific weight of the columns of gas rich and weak,respectively, in refrigerant vapor. Since the column of gas rich inrefrigerant vapor and flowing from the evaporator sections 10 and 11 tothe absorber coil 21 is heavier than the gas weak in refrigerant andflowing from the absorber coil 21 to the evaporator sections, a force isproduced or developed within the system for causing circulation of inertgas in the manner described.

From the vessel 20 enriched absorption liquid flows through a conduit 25and an inner passage 26 of a liquid heat exchanger 27 into the lower endof a vapor lift tube 28 of a generator or vapor expulsion unit 29. Thegenerator unit 29 comprises a heating flue 30 having the vapor lift tube28 and a boiler pipe 31 in thermal exchange relation therewith, as bywelding, for example. By heating generator unit 29, as by a gas burner32, for example, liquid from the inner passage 26 of the liquid heatexchanger is raised by vapor lift action through tube 28 into the upperpart of the boiler pipe 31. The liberated refrigerant vapor enteringboiler pipe 31 from the tube 28, and also vapor expelled from solutionin the boiler pipe, flows upwardly into an air cooled condenser 33provided with a plurality of heat dissipating members or fins 34.Refrigerant vapor is liquefied in the condenser 33 and returns to theevaporator sections 10 and 11 through the conduit 16 to complete therefrigerating cycle.

The weakened absorption liquid, from which refrigerant vapor has beenexpelled, is conducted from boiler pipe 31 through a conduit 35, outerpassage 36 of the liquid heat exchanger 27 and conduit 22 into the upperpart of the absorber coil 21. The lower end of the condenser 33 isconnected by conduit 37 to the gas circuit, as to the upper part of theabsorber coil 21, for example, so that any non-condensable gas which maypass into the condenser can flow to the gas circuit and not be trappedin the condenser.

In adapting the refrigeration system of Fig. 1 for use in therefrigerator cabinet 14 of Fig. 2, the evaporator sections 10 and 11 aredisposed in the thermally insulated interior 12 thereof, and the gasheat exchanger 18, which is indicated in dotted lines in Fig. 2, andother parts may be disposed at the rear of the cabinet. The horizontallydisposed evaporator sections 10 and 11 are connected in series relationwith inert gas from conduit 24 flowing through the upper evaporatorsection 10 in the presence of and in parallel flow with liquidrefrigerant which is introduced through conduit 16. From evaporator secton 10 inert gas then passes through the vertical connection 15 for flowthrough the lower evaporator section 11. Unevaporated refrigerant isalso conducted from evaporator section 10 through the connection 15 intothe lower evaporator section 11 and flows therein in the presence of andin parallel flow with the inert gas. It is to be understood, however,that inert gas and liquid refrigerant may pass each other in counterfiowrelation in the lower evaporator section 11, and liquid refrigerant maybe conducted thereto directly from a separate condenser section, ifdesired.

Since the inert gas flows successively through the evaporator sections10 and 11, the gas in the upper evaporator section contains a lesseramount of refrigerant vapor than the gas in the lower evaporator section11. The partial vapor pressure of the refrigerant is a gradient, so thatthe temperature of liquid refrigerant in the evaporator sections 10 and11 also is a gradient, the evaporating temperature of liquid being lowerin the upper evaporator section 10 which constitutes the freezingportion of the cooling unit.

In the refrigerator cabinet 14 of Fig. 2, the interior 12 thereof issubdivided into a plurality of compartments one above the other by ahorizontal partition 40 which is constructed to thermally insulate thecompartments from one another. The heat insulating partition 40desirably extends over the entire width of the interior of the cabinet,and from the rear wall toward the open front of the cabinet so thatcirculation of air between the spaces above and below the partition issubstantially'prevented when the door or closure member of the cabinetis in its closed position. The lower evaporator section 11 may bepositioned immediately beneath the insulating partition 40, and, sincethis evaporator section is the higher temperature section or portion ofthe cooling unit, it may be effectively utilized to cool air in thelower compartment 41. To provide adequate heat transfer surface, thecoils of the lower evaporator section 11 may have a plurality of fins 42secured thereto. The compartment above the insulating partition 40 isadapted to serve as a freezing section of the refrigerator cabinet 14 inwhich the lower temperature evaporator section 10 is positioned.

The freezing unit of the refrigerator is subdivided into an uppersection 43 and a lower section 44 by a horizontally disposed heatconductive member 45 with which the upper evaporator coil 10 isthermally associated. As shown, this is accomplished by arranging thelooped coil forming the evaporator section 10 in thermal exchangerelation with the upper side of the member 45. In addition, a horizontalplate 46 having downwardly depending flanges 47 is positioned over theevaporator section 10 in good thermal contact therewith; This may beaccomplished by providing clamping members 48 along the straightportions of the evaporator coil or section 10 that envelop the pipingand have flanges 49 which are secured, as by brazing, for example, tothe underside of the plate 46.

The upper section 43 of the freezing unit may be referred to as an icefreezing section adapted to receive ice trays for freezing water and thelike, the plate 46 being substantially flat and serving as a supportingshelf for such ice trays. The lower section 44 of the freezing unitdesirably is of greater depth than the upper portion 43 and may bereferred to as a frozen food section adapted to receive frozen foodpackages and other matter to be frozen. Since the low temperatureevaporator coil 10 is in good heat conductive relation with the heatconducting member 45 and also the plate 46, heat is effectivelyabstracted from ice trays positioned on the plate 46 and also frommatter stored in the frozen food section 44. Although not shown, asuitable closure member or members desirably may be provided at thefront opening of the freezing unit to close both the upper and lowerportions 43 and 44, respectively.

In accordance with the invention, the heat conducting member 45desirably is constructed as a cold accumulator having a hollow interiorwhich is filled with a solution that freezes at a low temperature. Sucha cold accumulator may comprise a pair of spaced apart plates which arerelatively close to one another and sealed at the peripheral edgesthereof to provide a hollow interior for holding a substance, such as aeutectic solution, for example,5 which freezes at a temperature of aboutl0 to --l C.

During the periods when the ice freezing section 43 is under a smallload, the low temperature evaporator section 10 is effectively employedto abstract heat from the body of eutectic solution in the member 45,thereby lowering the eutectic solution to a very low temperatureadequate to maintain frozen food in the frozen food section 44 wellbelow the freezing temperature. When ice trays containing water to befrozen are placed on the supporting shelf or plate 46, the load on theice freezing section 43 is increased. With a substantial increase in icefreezing load, the temperature of the low temperature evaporator section10 may increase to a value which is not far below the freezingtemperature of water.

If the cold accumulator 45 were not provided, the evaporator coil 10alone would have to be relied upon to keep frozen food in the frozenfood section at a safe refrigerating temperature. However, a substantialincrease in ice freezing load may cause the evaporator coil 10 to riseto a temperature which is not far below the freezing temperature andwhich will remain substantially constant for a considerable length oftime during the entire ice freezing period. Under such conditions theability of the evaporator coil 19 alone to maintain frozen food at asafe refrigerating temperature is decreased, and under severe operatingconditions the evaporator section 10 may be ineffective to keep frozenfood at a sufnciently low temperature.

By providing the cold accumulator 45, undesirable increase intemperature of the frozen food section 44 is avoided, particularlyfrozen food stored in the uppermost part of such freezing section. Inaccord with the invention the total melting heat of the cold accumulator45 desirably is balanced so that the eutectic solution will remainfrozen during the interval of time that water stays in a liquid state inthe ice trays. The cold accumulator.

desirably may be oversize and larger than actually necessary to insurethat it will take care of the most severe load on the ice freezingsection 43. However, the cold accumulator should not needlessly be madeunduly large because this reduces the maximum amount of storage spacemade available for ice trays, frozen food and other matter adapted to beplaced in the freezing sections 43 and 44. When the eutectic solution inthe cold accumulator is frozen or charged at the time ice trayscontaining water are positioned in the ice freezing section 43, thedecrease in temperature of the supporting shelf or plate 46 that wouldotherwise occur is substantially reduced, thereby accelerating the rateat which ice is formed to a relatively high extent.

Further, it will be seen in Figs. 1 and 2 that evaporator section 11receives liquid refrigerant from evaporator sectlon 10. During periodsof low load on evaporator section 10 the temperature of the coldaccumulator 45 becomes reduced so that, upon subsequent increase in loadon the low temperature evaporator section 10, the cold accumulator 45 ineffect constitutes a source of supply of refrigeration. In this way thequantity of liquid refrigerant necessary in evaporator section 10 tosatisfy such increased load is reduced, and the liquid refrigerant notrequired in evaporator section 10 to produce refrlgeratlon therein flowsby gravity into the higher temperature evaporator section 11 and madeavailable in the latter. Thus, under the most adverse operatingconditions encountered when the load on the low temperature evaporatorsection 10 is increased, an adequate supply of liqu d refrigerant forthe higher temperature evaporator section 11 is insured to maintain asafe refrigerating temperature in the lower compartment 41 in whichfoods are kept at a temperature above the freezing temperature.

Figs. 4 to 7 inclusive illustrate another embodiment of the invention inwhich there is provision for maintaining a frozen food section 44a at asafe refrigerating temperature even when the load on the ice freezingsection 43a is increased at times.

As best shown in Figs. 4 and 7, the cooling unit comprises a shell orcasing 50 having a top wall 51, bottom wall 40a and side walls 52. Theshell extends across the entire width of the interior 12a of the cabinet14a, and from the rear wall 53 toward the open front of the cabinet sothat circulation of air between the space 41a and freezer sections 43aand 44a is substantially pre-- vented when the door of the cabinet, notshown, is in its closed position. As in the embodiment first described,one or more closure members desirably may be provided at the frontopenings of the freezer portions 43a and 44a.

The low temperature evaporator a is disposed in the upper part of theshell 50, as will be described more fully hereinafter, while the highertemperature evaporator 11a is positioned in the upper part of the lowercompartment or space 41a. The evaporator sections 10a and 1111 areadapted to be connected to other parts of an absorption refrigerationsystem of the inert gas type and like that diagrammatically shown inFig. 1. However, the parts of the refrigeration system which are shownin Figs. 4, 5 and 7 differ from those illustrated in Fig. l in that ahorizontal gas heat exchanger 18a is provided to which the evaporatorsections 10a and 11a are connected.

In Figs. 4 and 5 inert gas weak in refrigerant flows from the upper endof the absorber coil through a conduit 21a, an inner passage of thehorizontal gas heat exchanger 18a and conduit 24:: to which is connectedone end of the evaporator section 10a, as indicated at 54 in Fig. 5.Liquid refrigerant from the condenser is also conducted to the same endof the evaporator section 10a through a conduit 16a, so that liquidrefrigerant passes through the upper evaporator section 19a in parallelflow with inert gas. Both liquid refrigerant and inert gas pass from theupper evaporator section 10a at 55 through the vertical connection a forparallel flow in the lower evaporator section 11a which is provided withheat transfer members or fins 42a.

Inert gas rich in refrigerant flows from the higher temperatureevaporator section 11a at 56 into an outer passage of the gas heatexchanger 18a and thence through a conduit 19a which is connected at itslower end to the absorber vessel in a manner similar to the conduit 19in Fig. 1. As best shown in Fig. 4, the conduit 21a for inert gas weakin refrigerant envelops and surrounds the conduit 19a through whichinert gas rich in refrigerant returns to the absorber. In order toprecool liquid refrigerant conducted to the upper evaporator section 10athrough the conduit 16a, the latter is connected at spaced apart regionsto the outer passage of the gas heat exchanger lSa by conduits 57, asshown in Fig. 5. In this way natural circulation of inert gas from theouter passage of the gas heat exchanger 18 takes place through a part ofconduit 16a and evaporation and diffusion of refrigerant into inert gastakes place, thereby taking up heat from liquid refrigerant before beingintroduced into the evaporator section 10a.

In order to position the evaporator sections 10a and 11a and shell 50 inthe thermally insulated interior 12a of the cabinet 14a, the rear wall53 is formed with an opening 58 defined by a rectangular frame 59 whichmay be formed of wood, for example. A cover or closure member 60 for theopening, which contains insulating material 61 and in which the gas heatexchanger 13a is embedded, is arranged to bear against a gasket 62 ofsuitable insulating material and is removably secured at 63 to the rearwall 53.

The top wall 51 of the shell 50 comprises spaced apart plates 46a and45a, and the low temperature evaporator section 10a is formed to providetwo looped coils 10a and 10a, each of which is in thermal exchangerelation with one of the plates 45a and 46a. As best shown in Fig. 5,each looped coil 10a and 10a" includes spaced apart straight portionswhich are more or less parallel to one another and connecting bends,thereby forming a number of U-shaped pipe portions which are seriallyconnected to one another. Further, the legs of certain U-shaped elementsor pipe portions are disposed between the legs of other U-shapedelements to provide a compact arrangement of the looped coils 10a and10a.

As best shown in Fig. 6, the looped coil 10a is arranged in thermalrelation with the upper side of the plate 45a, and the looped coil 10a"is arranged in thermal relation with the underside of the plate 46a. Itwill be seen that the diameter of the piping forming the looped coil 10ais smaller than that of the piping forming the looped coil 10a", andthat the horizontal planes tangential to the top and bottom portions ofthe looped coil 10a are at levels between the horizontal planestangential to the top and bottom portions of the looped coil 10a". Thelooped coils 10a and 10a" may be arranged in good heat conductingrelation with the plates 45a and 46a in any suitable manner, as byclamping members 48a which envelop the straight portions of the coilsand are secured to the spaced apart plates forming the top wall 51 ofthe shell 50.

Essentially, the spaced apart plates 45a and 46a form a container orvessel which desirably is filled with a suitable insulating material 64for thermally shielding the two portions 10a and 10a of the evaporatorsection 10a from one another. In order to obtain the compact arrangementof the looped coils 10a and 10a" in the manner just described, it willbe seen that the bottom plate 45a is formed with a depressed region 65immediately beneath looped coil 10a along the length thereof, as seen inFig. 6, so that each looped coil is out of physical contact and removedfrom the plate to which it is not thermally connected. In the embodimentbeing described it will be seen that a cold accumulator 45a is providedfor the frozen food section 44a.

In the operation of the embodiment being described, liquid refrigerantand inert gas weak in refrigerant first flow through the looped coil 10awhich is in thermal contact with the bottom plate 45a of the top wall 51of the cooling unit. With such arrangement strong cooling of the plate45a is effected which serves as the ceiling or roof of the frozen foodsection 44a, the bottom wall 40a of which is constructed to insulatesuch frozen food section from the lower food compartment 41a.

From the looped coil 10a liquid refrigerant and inert gas then flow inthe presence of each other into the looped coil 10a which is in thermalcontact with the upper plate 46:: of the top wall of the freezing unit.In this manner strong cooling of the plate 46a is also effected whichserves as a supporting shelf of the ice freezing section 43a of thefreezing unit. When the load on the ice freezing section 43a isincreased by placing ice trays containing water to be frozen on theplate 46a, the temperature of the looped coil or evaporator portion 10a"increases. However, such rise in temperature of the evaporator portion10a" does not adversely affect or cause any rise in temperature of thelooped coil or evaporator portion 10a, because liquid refrigerant andinert gas weak in refrigerant are continuously introduced into thelatter. Hence, the plate 45a will always be strongly cooled by thelooped coil 10a' to keep frozen food in the frozen food section 44a at asafe refrigerating temperature, irrespective of sudden increase in loadon the ice freezing section 43a.

Since the frozen food section 44a will be primarily employed for storingfrozen food packages, the load on the looped coil or evaporator portionwill be relatively small. Consequently, liquid refrigerant willpractically always be supplied to the looped coil or evaporator portion10a", and the inert gas which is introduced therein will not be too richin refrigerant vapor, so that the evaporator portion 10a will be quiteeffective to efiect cooling of the ice freezing section 43a for thepurpose of producing ice.

In the embodiment of Figs. 4 to 7 a cold accumulator 45b is provided forthe frozen food section 44b. It will be understood that the provision ofthe cold accumulator.

45b in Figs. 4 to 7 will act to restrict changes or variations intemperature of the frozen food section 44a, and this is particularlytrue when the operation of the refrigeration system is thermostaticallycontrolled responsive to a temperature condition of the air being cooledor temperature of an evaporator section. In such case the supply of heatto the generator unit is reduced from time to time to regulate therefrigerating effect produced by the evaporator sections. During theperiods when the heat input to the generator unit is reduced, the coldaccumulator 45b exerts a stabilizing influence and acts to maintain thefrozen food section 44a at a safe refrigerating temperature at alltimes.

Since the plate 46a and evaporator portion 10a" of the ice freezingsection 43a are thermally shielded from the evaporator portion 10a offrozen food section 44a, the cold accumulator 45b does not influence icefreezing in the ice freezing section 43a to any significant extent.

If it is desired to utilize the cold accumulator 45b to acceleratefreezing of ice in the ice freezing section 43a, heat conductive membersmay be provided which provide a thermal connection between the top plateof the cold accumulator and plate 46a. Such an arrangement is preferableto that of providing direct thermal contact between the plate 46a andtop wall of the cold accumulator, or between the looped coils 10a and10a". In certain instances it may be advantageous to provide the coldaccumulator on the plate 46a, so that ice trays containing water to befrozen can be placed thereon, or a second cold accumulator may beprovided on top of the plate 46a in addition to that shown in Figs. 4 to7 which is in thermal relation with the looped coil 10a. An arrangementin which a cold accumulator 450 is disposed at the top of the plate 46ais illustrated in Fig. 8; an an arrangement in which both the coldaccumulators 45b and 450 are employed is illustrated in Fig. 9.

In certain instances advantages are realized by providing a constructionin which the ice freezing section is located below the frozen foodsection of the freezing unit. Such an arrangement is shown in Fig. 10 inwhich the looped coil 10c is positioned at the roof or ceiling of thefrozen food section 440. The looped coil 10c is fixed to a plate 66which is insulated from the inner lining 67 of the cabinet interior 12cin any suitable manner. The bottom of the frozen food section 44c 15formed by a partition 40c constructed to be heat insulating, suchpartition also serving as the roof or ceiling of the ice freezingsection 430. The looped evaporator coil 10c" is in thermal relation withthe underside of plate 460 which serves as the supporting shelf of theice freezing section 430. The plate 460 and plate 68 closely adjacentthereto form a container or vessel in which the looped coil 10c" andanother looped coil 11c are disposed, the latter being in thermalcontact with the upper side of the plate 68. The looped coils 10c" and110 are thermally shielded from one another by suitable insulation 64c,and a plurality of members 69 are fixed to the underside of plate 68 toprovide a relatively extensive heat transfer surface to promoteeificient cooling of air in the space 41c by the looped evaporator coil110.

In the embodiment of Fig. 10, the looped evaporator coils are connectedin series whereby inert gas first flows through the uppermost loopedcoil 10c, then through the looped coil 10c and finally through thelooped coil 110 which constitutes the higher temperature evaporatorsection corresponding to evaporator section 11 in Fig. 1 and evaporatorsection 11a in Figs. 4 and 7. Hence, inert gas weak in refrigerantinitially flows through looped coil 10c which corresponds to looped coil10a in Fig. 6, and the cooling elfect produced by this looped coil isutilized to maintain the frozen food section 44c at a safe refrigeratingtemperature irrespective of changes in load on looped coil 10c" which isutilized to produce ice in the ice freezing section 43c. The operatingtemperature of the higher temperature looped coil 11c may be about C. orslightly below this value. In Fig. a cold accumulator 45d is providedfor the looped coil 100". A modification of the embodiment of Fig. 10 isillustrated in Fig. 11 in which a cold accumulator 45s is provided forthe looped coil 10c. In the modification shown in Fig. 12 both coldaccumulators 45d and 4512 are provided for the looped coils 10c" and10c, respectively.

The cold accumulators may employ any well known eutectic solution havinga sufficiently low freezing temperature, so that heat can be abstractedat a low temperature which is below 0 C., for example. Varioussubstances can be employed to provide the eutectic solution desireddepending upon the operating temperatures of the different sections ofthe cooling unit. It will be understood that homogeneous substanceshaving a melting point below the freezing temperature of water can beemployed as well as eutectic solutions.

Modifications of the embodiments of our invention which we havedescribed will occur to those skilled in the art, so that we desire ourinvention not to be limited to the particular arrangements set forth andintend in the claims to cover all modifications which do not depart fromthe spirit and scope of the invention. However, the provision of alooped coil which is disposed essentially in a single horizontal planeand heat conductively connected to horizintally disposed members, in amanner dlO generally like that shown, for example, in the embodiment ofFigs. 4, 5 and 6, is being claimed in copending application Serial No.324,530, filed December 6, 1952.

What is claimed is:

1. In a refrigerator comprising a cabinet having a thermally insulatedinterior divided into a freezing compartment and a higher temperaturefood storage compartment, an absorption refrigeration system of theinert gas type having a circuit for circulation of inert gastherethrough comprising evaporator structure including a low temperatureevaporator arranged to produce a refrigerating effect in said freezingcompartment and a higher temperature evaporator arranged to produce arefrigerating effect in said food storage compartment, means forsupplying liquid refrigerant to said evaporators for evaporation thereinin the presence of the circulating inert gas to produce saidrefrigerating eifects, and means for distributing the refrigeratingeffect capable of being produced by said evaporator structure duringoperation of the system, said distributing means including a coldaccumulator heat conductively connected to said low temperatureevaporator, said cold accumulator containing a ffuid whose temperaturebecomes reduced during periods of low load to produce a source of supplyof refrigeration which is available upon increase in load on said lowtemperature evaporator during operation of the system to reduce thequantity of liquid refrigerant necessary in the latter to satisfy suchincreased refrigcrating load and increase the quantity of refrigerantimmediately available in said higher temperature evaporator.

2. Apparatus as set forth in claim 1 in which said means for supplyingliquid refrigerant includes connections for conducting refrigerant tosaid low temperature evaporator for flow therethrough and said highertemperature evaporator is connected to receive refrigerant from said lowtemperature evaporator, said cold accumulator serving to reduce thequantity of liquid refrigerant necessary in the low temperatureevaporator upon increase in load on the latter during operation of thesys tem and making such refrigerant immediately available in the highertemperature evaporator.

3. Apparatus as set forth in claim 1 in which the fluid in said coldaccumulator comprises a body of congealable fluid like an eutecticsolution, for example, such cold accumulator heat conductively connectedto said low temperature evaporator being disposed in the interior of thecabinet and providing a supporting surface for matter to be refrigeratedin said freezing compartment.

4. Apparatus as set forth in claim 1 in which said low temperatureevaporator comprises a horizontally extending element disposed in theinterior of said cabinet and said cold accumulator comprises a flathorizontlly extending container in thermal contact with said lowtemperature evaporator, the fluid in said container comprising a body ofcongealable liquid like an eutectic solution, for example, and partitionmeans to provide said freezing compartment and food storage compartmentwhich includes said container.

5. Apparatus as set forth in claim 1 in which said low temperatureevaporator is employed for ice producing purposes, said low temperatureevaporator comprising a horizontally extending member disposed in saidcabinet and said cold accumulator and fluid therein comprising a vesseland a body of congealable liquid held therein like an eutectic solution,for example, said cold accumulator being in thermal contact with saidmember and providing a supporting surface for shallow trays in which iceis adapted to be produced.

References Cited in the file of this patent UNITED STATES PATENTS2,073,123 Smith Mar. 9, 1937 2,257,924 Vretman Oct. 7, 1941 2,345,453Brace Mar. 28, 1944 2,428,312 Herbener Sept. 30, 1947 2,589,550 IwashitaMar. 18, 1952

